What are the sign that peugot 406 1998 model can give if the timing chain is weak .

You don't say what the problem is- what the symptoms are- a worn timing chain will make the engine run rough- and it might rattle around in there- I say "might" because usually a timing chain will last a long time- as long as the rings and the bearings- so you may not need one until it's time to rebuild the whole engine- just hope it's something easier to replace than a timing chain-